1. Field of the Invention
The present invention relates generally to temperature estimation, and in particular, to estimating ambient air temperature with an engine control module when ambient temperature sensors are unavailable.
2. Background Art
Engines, such as compression-ignition engines, are used in a number of applications, from industrial to automotive. Many of the engines, especially in automotive applications, include an engine control module.
The engine control module relies on a number of inputs to make calculations and to perform other tasks. The ability to make desired calculations can be effected by failure of the inputs sources, which commonly are sensors, or simply by the failure to provide any input at all for making the desired calculation.
As such, it is desirable to provide the engine control module with the ability to make the desired calculation from the inputs actually available to the engine control module, even if the available inputs are not directly related to the desired calculation. Such calculations are commonly referred to as indirect estimates as they are based on indirect inputs, and not inputs directly related to the calculation.
Automotive manufacturers, for example, will not typically provide an ambient air temperature sensor for directly sensing ambient air temperature outside of the engine compartment. Consequently, engine control module manufacturers are forced to provide engine control modules with an ability to indirectly estimate the ambient air temperature from the inputs which are available the engine control module.